This is a cashel, a type of ringfort defined by its stone construction rather than earthen banks, and the one at Castlesheenaghan is a particular example of how prehistory and agriculture can become so entangled as to be almost inseparable. A modern gate now fills what was probably the original eastern entrance, and a barn occupies the south-eastern interior, while a shed leans against the outer face where part of the wall has been cut away to accommodate it.

The cashel itself is a roughly circular raised area, measuring approximately 28 metres north to south and 27 metres east to west, enclosed by a drystone wall whose dimensions tell a story of gradual modification. The wall varies considerably: at its narrowest, on the western side, it is about 1.7 metres wide, but where the inner face has slumped into a sod-covered slope over the centuries, the overall width reaches around 4 metres at both north and south. The wall still stands to an external height of 1.7 metres on the northern side, and short stretches of intact internal stone facing survive at the south-east and west. A modern house and garden border the cashel to the west, and sycamore and hawthorn trees have taken hold around the perimeter, giving the whole structure a slightly overgrown, half-obscured quality even as farm activity continues within it. Two gated breaks in the wall, one at the east and one at the north-north-east, now serve agricultural purposes, though they may follow or have influenced the line of much older openings.